1. Field of the Invention
The invention relates to novel polyaddition compounds of disecondary diamines and of polyisocyanate mixtures comprising uretdione diisocyanates and based on hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI).
2. Description of the Background
DE-OS 30 30 572 (equivalent to U.S. Pat. No. 4,483,798) describes polyaddition products which contain uretdione groups and have since acquired economic importance for the preparation of PUR powders which are free from blocking agents. These polyaddition products are of an isophorone diisocyanate, which is free from isocyanurate groups and contains uretdione groups, reacted with a diol, the addition product thus obtained optionally being completely or partiy reacted with monoalcohols or monoamines.
Corresponding polyaddition products based on a uretdione, containing NCO groups of hexamethylene diisocyanate (abbreviated to HDI-uretdione in the following) are not possible, as described in EP 0 478 990 (p. 2, lines 38-40) (equivalent to U.S. Pat. No. 5,143,994).
Such products would represent a welcome enrichment of the PUR powder hardeners which already exist, since with these it would be possible for PUR powders to be tailor-made in terms of flexibility in a simple manner.
The object of the present invention was thus to provide polyaddition compounds which are based on HDI-uretdione and are suitable as PUR powder hardeners.
It has been possible to achieve is object with the polyaddition compounds according to the invention described below.